2. The Directory Server Access Control Model
3. Understanding the Directory Server Schema
4. Directory Server Index Databases
5. Understanding Directory Server Plug-Ins
6. Directory Server Replication
Overview of the Directory Server Replication Architecture
Basic Replication Architecture
Directory Server Change Processing
Historical Information and Conflict Resolution
What is a Replication Conflict?
Purging Historical Information
Schema Replication Architecture
Replication Status Definitions
Full Update Status and Bad Generation ID Status
Safe Read Mode and Replication Groups
Assured Replication Connection Algorithm
Assured Replication and Replication Status
Assured Replication Monitoring
Fractional Data Set Identification
Fractional Replication Filtering
Fractional Replication and Local Operations
How the External Change Log Works
Porting Applications that Rely on Other Change Logs
Differences Between the ECL and the LDAP Change Log Draft
Additional Differences Between the ECL and the Sun DSEE Retro Change Log
API for Compatibility With the LDAP Change Log Draft and the Sun DSEE Retro Change Log
Limitations of the Compability API
Change numbers uniquely identify changes that are made on an LDAP directory server. Change numbers also provide a consistent ordering of changes. The change number order is used to resolve conflicts and to determine the order in which forwarded changes should be replayed.
A change number consists of the following elements:
Time stamp, in milliseconds. Time stamps are generated using the system clock. The change number is also generated such that each change number is always greater than all the change numbers that have already been processed by the server. Constantly increasing change numbers guarantees that operations that depend on previous operations are consistently replayed in the correct order. An example of an operation that depends on a previous operation is a modify operation that directly follows the add operation for that entry.
Sequence number. A sequential number, incremented for each change that occurs within the same millisecond.
Replica identifier. A unique integer identifier that is assigned to each replica in a topology. (A replication topology is the set of all replicas of a given data set. For example, the replication topology for example.com might be all copies of the dc=example,dc=com suffix across a directory service.)
The replica identifier ensures that two different servers do not assign the same identifier to two different changes. In a future directory server release, an algorithm might be used to assign replica identifiers automatically.